Augmented hydrostatic extrusion of fine wire

ABSTRACT

A control system for hydrostatic extrusion apparatus includes a first controlled tension wire reservoir stage for continuously receiving extruded wire from an extruder press and a positive drive capstan for pulling wire out of the first reservoir stage at a controlled velocity. Wire from the positive drive capstan moves into a second controlled tension reservoir stage and then to a wire reeling apparatus. The extrusion press pressure is controlled in response to a change of length of wire in the first reservoir with a control mode which tends to equalize extrusion speed with the drive capstan speed. The wire reeling apparatus is driven at a speed basically controlled in relation to capstan speed, but precisely and rapidly controlled in response to the amount of wire in the second reservoir, and thus instantaneously independent of the wire extrusion speed, with a control mode which, within reservoir capacity limits, equalizes coiling speed with the drive capstan speed. Extrusion speed control by control of press pressure is augmented by also controlling a pulling force which pulls wire from the press. Thus, the pulling force under appropriate conditions may be either increased or decreased in order to respectively add to the increase or decrease of the extrusion speed. Control means are provided to interrelate augmentation drawing forces and hydrostatic extrusion pressures in such a manner that under the varying conditions which might be experienced, a proper combination of pulling force and hydrostatic extrusion pressure would be provided. In a preferred embodiment of the invention, the relationship between capstan speed and reel speed is determined from the position of the drawing force-applying reel of the first reservoir and through electronic computation means and servo loop controls. The relationship between applied draw force, applied extrusion pressure and capstan speed may be programmed in any desired manner.

United States Patent [1 1 Dihrell Feb.4,1975

[ 1 AUGMENTED HYDROSTATIC EXTRUSION OF FINE WIRE James W. Dibrell, Malibu, Calif.

[73] Assignee: Microwire Corporation, Allentown,

[22] Filed: Jan. 2, 1973 [21] Appl. No.: 320,088

[75] Inventor:

Primary Examiner-Richard J. Herbst Attorney, Agent, or Firm-Ostrolenk, Faber, Gerb & Soffen [57] ABSTRACT A control system for hydrostatic extrusion apparatus includes a first controlled tension wire reservoir stage for continuously receiving extruded wire from an extruder press and a positive drive capstan for pulling wire out of the first reservoir stage at a controlled velocity. Wire from the positive drive capstan moves into a second controlled tension reservoir stage and then to a wire reeling apparatus. The extrusion press pressure is controlled in response to a change of length of wire in the first reservoir with a control mode which tends to equalize extrusion speed with the drive capstan speed. The wire reeling apparatus is driven at a speed basically controlled in relation to capstan speed, but precisely and rapidly controlled in response to the amount of wire in the second reservoir, and thus instantaneously independent of the wire extrusion speed, with a control mode which, within reservoir capacity limits, equalizes coiling speed with the drive capstan speed. Extrusion speed control by control of press pressure is augmented by also controlling a pulling force which pulls wire from the press. Thus, the pulling force under appropriate conditions may be either increased or decreased in order to respectively add to the increase or decrease of the extrusion speed. Control means are provided to interrelate augmentation drawing forces and hydrostatic extrusion pressures in such a manner that under the varying conditions which might be experienced, a proper combination of pulling force and hydrostatic extrusion pressure would be provided. In a preferred embodiment of the invention, the relationship between capstan speed and reel speed is determined from the position of the drawing-force-applying reel of the first reservoir and through electronic computation means and servo loop controls. The relationship between applied draw force, applied extrusion pressure and capstan speed may be programmed in any desired manner.

27 Claims, 8 Drawing Figures PATENIED FEB 386131.481

SHEET 3 OF 3 AUGMENTED HYDROSTATIC EXTRUSION OF FINE WIRE FIELD OF THE INVENTION This invention relates to the continuous production of elongated products by hydrostatic extrusion, and more specifically relates to a novel control process and control apparatus for application to hydrostatic extrusion.

THE PRIOR ART The production of material having a relatively small cross-section, particularly metals with a cross-section sufficiently small that they can be coiled, is conventionally carried out by several different processes. One is the drawing process in which a continuous wire filament from an initial billet is passed through serially arranged dies, each of which reduces the area of the wire being drawn, until the desired cross-section is reached. Note that the wire can have any desired cross-section, and may be rectangular, hollow tubular, circular, or the like. Moreover, the wire may be formed of an inner core with one or more outer sheaths of diverse material. All of these are hereinafter generically referred to as wire.

The conventional wire drawing process has many obvious disadvantages including, but not limited to, the need for very expensive equipment, relatively high downtime due to occasional failures of the wire at any one of the drawing stages, and the need for highly skilled line attendants. Moreover, it is extremely difficult to use the drawing process to produce very fine metallic wire, such as metal wire having a diameter less than about mils (0.010 inches) because the drawing force must be kept well below the breaking strength of the wire.

Wire products are also conventionally formed by a hot extrusion process in which hot materials are forced through an extrusion die by a ram. This process, however, is not applicable to the extrusion of small diameter wire.

To avoid the many disadvantages of the commercial wire drawing process and the hot extrusion process, attempts have been made to apply hydrostatic extrusion techniques to the formation of metallic wire and other elongated filament products including, but not limited to, materials such as metallic oxides, carbides and other cermets, and graphite. The application of hydrostatic extrusion techniques has been described in the publication EXPERIMENTAL STUDY OF HYDROSTATIC EXTRUSION by Avitzur and Sortais, ASME Paper No. 65-WA/MET-2, Journal of Basic Enginerring, Transactions ASME, Series D, Volume 88, No. 3, September 1966, pages 658-668, presented at the Annual Meeting November 7-11, 1965. The hydrostatic extrusion process is also described in US. Pat. No. 2,558,035 to Bridgman. In this patent a billet to be extruded is loaded into a fluid-filled chamber and a pointed end of the billet is passed through an opening in an extrusion die, sealing the opening. The pointed end is then connected to apparatus in the receiving portion of the chamber which exerts a draw stress on the wire. The fluid in the chamber is then pressurized by a suitable piston apparatus to increase the fluid pressure, thus exerting a hydrostatic pressure on the billet of 100,000 to 400,000 p.s.i. and even higher. The application of this pressure plasticizes the billet, thereby substantially reducing or even eliminating a draw stress (or pulling force) to effect a relatively high reduction in wire area.

The relationship between hydrostatic pressure and pulling force is disclosed in the above paper by Avitzur and Sortais as well as in the U.S. Pat. No. 3,328,998 to Sabroffet al. This patent discloses the quantitative rela' tion between pulling stress and pressure for different die designs when extruding relatively thick aluminum wire, for example, circular wire having a final diameter of 40 mils. The stated mode of control of Sabroff et al. US. Pat. No. 3,328,998 is to maintain a constant pressure in the hydrostatic extrusion chamber at a level less than the yield strength of the extruded wire, combining this pressure with the pulling force on the wire lead extending through the extrusion die. This pulling force is also less than the yield strength of the wire. The patent then discloses that this combination of two forces generates a condition under which the wire is extruded through the die while the pulling force also remains constant.

More recent work on the hydrostatic extrusion process, aimed at the production of fine beryllium wire (down to 5 mils thick), at a speed of 2, l 00 feet per minute is described in a technical report by Richardson et al., entitled PROTOTYPE PRODUCTION PROCESS FOR FABRICATION OF WIRE AND TUBING BY HYDROSTATIC EXTRUSION-DRAWING, Technical Report AFML-TR-70-82, United States Air Force Contract No. F336l5-68-C-l 197, Battelle Memorial Institute, May 1970. In the above report, the drawing apparatus includes a coiling reel driven by a variablespeed drive motor operating through an electromagnetic clutch.

The drive-motor controls are preset to stabilize the desired'drawing speed and the electromagnetic clutch controls are preset to establish the output torque level required to maintain the desired draw stress. A lead wire on the coiling reel is attached to a pointed end of the billet to be extruded, which end protrudes through the die in the extrusion chamber. Fluid is then loaded into the extrusion chamber, and the fluid pressure and draw force are manually adjusted to values need to initiate extrusion of the wire. Once extrusion starts, draw stress and pressure are manually adjusted to establish steady running conditions, and to adjust the system due to changes in other variables, such as viscosity of the fluid, temperature changes, and the like.

The process described above requires extreme manual dexterity on the part of the operator. So long as relatively thick high-strength material is being extruded, it is conceivable that an operator can respond quickly enough to changes in extrusion speed to adjust the pulling stress and pressure without either run-out (an uncontrollable, virtually explosive discharge of the material being extruded) or physically breaking the wire being extruded through an excessive pulling stress. However, when very thin and/or relatively soft materials are to be extruded, this manual control has not been found to be possible.

As will be later seen, the present invention allows the production of high purity, relatively soft metals such as gold and aluminum, as well as the harder metals such 1,000,000 feet or more of 1 mil wire, at speeds adjustable from less than 100 feet per minute to greater than 5,000 feet per minute. The wire produced also has exceptionally smooth and flawless surface characteristics and does not have the deep longitudinal die marks and pits that are typically observed in fine wire produced by drawing.

BRIEF SUMMARY OF THE INVENTION In accordance with the present invention, a control arrangement is provided whereby the functions of extrusion of the wire and coiling of the wire are maintained at the same average rate but are provided with a second order degree of control independently of one another. Thus the wire from the extrusion press moves into a first wire storage stage or reservoir and then to a positive drive device which pulls the wire according to a desired speed program, from start-up to normal operation extrusion speeds.

In a steady state condition, the speed of the capstan wheel is preset and kept constant. The purpose of the first portion of the control system is to maintain the extrusion velocity equal to the substantially steady coiling speed of the capstan. Whenever the extrusion velocity is higher or lower than that of the programmed capstan speed, wire is either loaded into or withdrawn from the first wire storage stage and corrective extrusion speed signals are applied to the extrusion press. Similarly, the wire leaves the positive drive device (which may be a driven capstan wheel) at a constant speed, and is supplied to the second wire storage reservoir at the said constant speed. The speed with which the wire is ultimately coiled is then controlled depending upon whether the wire is being stored or withdrawn from the second storage stage. If additional quantities of the wire are being stored in the second storage reservoir, an appropriate signal increases the coiling speed. If, on the other hand, the wire is being withdrawn from the secnd storage stage, the coiling speed of the final coiler is automatically reduced. By separating the control of the extrusion and coiling functions, it now becomes possible, for the first time, to extrude long runs of very fine wire, for example, gold and aluminum wire with thicknesses of 1 mil and less, at high speed.

In accordance with a further feature of the invention, the pulling force tending to pull wire from the extrusion press is modified in order to increase or decrease extrusion speed. Thus, control of press pressure to change extrusion speed is augmented by the further control of pulling force. Pulling force control can be automatically adjusted in the first wire storage stage which receives wire from the extrusion press. Thus, the first wire storage stage may consist of a storage dancer and may have a V shape so that the tension on the wire in the dancer, due to the movable dancer wheel weight, increases when wire is withdrawn from the dancer and the wheel moves up (to increase the V-shaped angle), and decreases when wire is loaded into the dancer, and the wheel moves down (to decrease the V-shaped angle). Consequently, the pulling force tending to pull wire from the extrusion press inherently and without time lag tends to correct wire speed in the proper direction in order to bring about a matching of extruded wire speed to the positive drive speed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 schematically shows a conventional hydrostatic extrusion system.

FIG. 2 is a block diagram of the control system of the present invention.

FIG. 3 schematically shows one embodiment of a wire path which could be followed by the wire handling apparatus in carrying out the control scheme of FIG. 2.

FIG. 4 is a perspective diagram of a positive drive capstan which could be used in FIGS. 2 and 3.

FIG. 5 illustrates. in perspective view, one ofthe wire storage elements of the wire path of FIG. 3.

FIG. 6 illustrates one manner in which an electrical signal can be developed from the wire storage portion of FIG. 5, which signal is related to a function of the velocity of the wire in the storage system.

FIG. 7 schematically illustrates the manner in which extrusion press pressure is controlled by signals developed from the circuit of FIG. 6.

FIG. 8 schematically illustrates the novel V-shaped dancer arrangement for receiving the wire from the hydrostatic extruder and which automatically increases or decreases pulling force in an endeavor to assist in properly changing the extrusion speed.

DETAILED DESCRIPTION OF THE DRAWINGS Referring first to FIG. 1, there is shown a presently known type of hydrostatic extrusion press for the hydrostatic extrusion of metallic wire. The press consists of an actuating cylinder 10 which contains a piston 11 having an extending stem 12. components 10, 11 and 12 are circular in section and have a conventional design. Stem I2 is movable into and is snugly fitted within fluid-filled, high-pressure cylinder 13 which contains the billet or stock to be extruded. In FIG. 1 the billet shown in the form of a wire coil 14. The end of cylinder 13 is closed by an extrusion die assembly I5 which may consist of a conventional die stack removably held in place by ring 16. The extrusion die assembly contains a central die orifice 17 of standard and well-known design, which has a cross-section corresponding to the crosssection of the product to be extruded. While any desired cross-section could be used, the extruded product will hereinafter be assumed to be circular in crosssection.

Cylinders 10 and 13 are suitably supported relative to one another by a support casing 20, which may be of any desired design and which is supported in any desired manner.

The volume 21 behind piston 11 is filled with a fluid which may be pressurized, typically to a pressure between 1,000 and 10,000 p.s.i. by the pump 22, which is, in turn, driven from variable speed motor 23 which is energized from terminals 24 and 25. The ratio of the diameters of piston 11 to stem 12 is chosen to obtain the desired pressure amplification in chamber 26 within cylinder 13. Thus:

P26 P21 X u u where p and p are the pressures in chambers 21 and 26, respectively, while D and D are the diameters of piston 11 and stem 12, respectively. When the pressure p21 is in the range between 1,000 and 10,000 p.s.i., and the pressure in chamber 26 is to be from 50,000 p.s.i. to 500,000 p.s.i., the ratio of diameters I), and D will be between about 3.3 and which are easily met design parameters.

The coil 14 of stock to be extruded is provided with a pointed end which is threaded through die opening 17 and attached to a suitable lead wire by cementing, or the like. This lead wire and the wire ultimately extruded through die 17 passes around rotatable idler wheel 30 which is rotatably mounted on a fixed bearing 31, with the periphery ofwheel 30 preferably placed on the axis of die opening 17. Wheel 30 is used to change the direction of movement of the extruded wire in a convenient manner, and also provides means for precise measurement of the draw stress applied to the wire at the die exit. The wire is then coiled on a wire receiving spool 32 which is driven by variable speed motor 33. Motor 33 has suitable input terminals 34 and 35.

The extrusion ratio, defined as the ratio of the crosssectional area of coil 14 before extrusion to its crosssectional area after extrusion through die 15 may be between 1.521 and 1000:], corresponding to reductions in diameter from between 1.211 and 33:1, respectively.

The apparatus of FIG. 1 could, theoretically, reduce a 6 inch slug of material 0.5 inches in diameter, to 125,000 feet of 0.001 inch diameter wire in four extrusion passes. Thus, the billet may be first reduced in diameter by a factor of 10 to a product having a diameter of 0.050 inches and a length of 50 feet. This product would then be coiled (to fit into chamber 26 without requiring a chamber of unusual length), and then reduced in diameter by a factor of 5. Thus, in the second extrusion step, the product will have a diameter of 10 mils and a length of 1,250 feet. This product could then be coiled and reloaded into chamber 26, and reduced in diameter by a factor of 4 to have a length of 20,000 feet and a diameter of 2.5 mils. A final reduction could reduce the diameter from 2.5 mils to 1.0 mil with a length of 125,000 feet.

The apparatus of FIG. 1 operates as follows:

The product to be extruded is loaded into chamber 26 and the end thereof is pointed so that it protrudes through die opening 17 and is attached to a lead wire extending around wheel 30 and fastened to coiler 32. Pump 22 is then driven by motor 23 to begin to pressurize chamber 21, thereby moving stem 12 to the right to pressurize the fluid, such as a suitable oil, within chamber 26. This causes the seating of the wire lead within the die opening 17 to seal the chamber. As the pressure within chamber 26 is increased, the material of coil 14 ultimately becomes sufficiently plasticized to begin to escape through the die 15, this being termed the breakthrough of the extrudate. The application of a pulling force to the wire being extruded by the motor driven coiler 32 will decrease the magnitude of this breakthrough pressure.

A further increase in pressure in chamber 26 (without reference to changes in extrusion speed) may reach run-out pressure at which the extruded material escapes through the die 15 at a very high and uncontrolled speed, in the manner of an explosive discharge of material. Note that run-out pressure is independent of the magnitude of pulling force caused by coiler 32.

It has been found that the extrusion of substantial lengths of wire of small diameter and relatively low strength will usually fail because of the difficulty of synchronizing the extrusion speed of the wire leaving the die 15, with the coiling speed at which coiler 32 coils the wire being extruded. These two speeds are substantially independent of one another. Thus the extrusion speed depends on the joint action of the pressure within chamber 26 and the force pulling wire out of the die 15, while the coiling speed will depend on the angular speed of coiler 32 and the radius of the coil at any instant. Perfect synchronization, if obtained, will be disturbed quickly. For example, extrusion speed will change, due to small fluctuations in press pressure, due to any of a large number of causes, such as temperature change and the like. The coiling speed might vary due, for example, to unintended changes in voltage at terminals 34 and 35, the build up of coil layers. and the like.

Given the difficulty in synchronizing the speeds ofextrusion and coiling, when the coiling speed is greater, it will quickly result in fracture of the extruded wire, especially if the wire has a low breaking force (for example, less than 50 grams). Conversely, if the extrusion speed is greater than the coiling speed, an unavoidable tangle will result in a few seconds since the wire which may be moving at the order of 1,000 feet per minute is not being properly coiled.

In the past, efforts have been made to control the process by having an operator manually control the voltage applied to the drives for pump 22 and coiler 32 in an effort to synchronize extrusion speed and coiling speed. The extreme concentration required to properly operate even for one minute limited the process to applications in which relatively strong wire is being extruded, so that it could withstand relatively large breaking force.

FIG. 2 shows, in block diagram form, the control system which can be applied to the apparatus of FIG. 1 to enable the high speed production of thin and fragile wire. In FIG. 2, the extrusion press is shown schematically as the press 40 having a pressure control element 41 (corresponding, for example, to components 22 and 23 in FIG. 1). The extruded wire from press 40 is shown in the double lines in FIG. 2 and first enters a wire storage and draw tensioner stage 42. Stage 42 may be of any desired construction and could, for example, be a conventional type ofdancer" reservoir which will store more or less wire, as needed, due to continuous differences in the velocity of wire entering and leaving the storage region 42. The use of the storage stage 42 permits a relatively constant force to be applied to extruded wire issuing from press 40, even though the extruded wire velocity differs from the wire velocity at other portions of the system.

The extruded wire then enters a positive wire drive stage 43 which tends to pull the wire with a predetermined velocity which may be either preset at a constant level or programmed automatically or manually from start-up to steady state operation. Thus the positive wire drive may take the form ofa capstan around which the extruded wire is coiled for one or more turns, with a frictional driving connection being made between the capstan surface and the wire. The capstan type drive will be later described in connection with FIG. 4. The wire pull velocity is then appropriately controlled from a velocity control system 44-48-41.

Wire from positive drive 43 is then supplied to a second wire storage stage 45, which also provides reeling tension and which may be constructed in a manner similar to storage stage 42. The wire is then coiled in wire reeling stage 46 (equivalent to coiler 32 of FIG. 1) which is, in turn, driven by reeling velocity control system 47-44, which includes motor 33 in FIG. 1.

The interposition of positive wire drive 43 breaks the dependency between control of coiling speed and control of extrusion speed, and allows the two speeds and the two tensions to be independently measured and independently controlled, as well as independently buff ered within the capacity ranges of storage stages 42 and 45. Thus, extrusion wire speed may now be controlled by measuring the extrusion speed against the positive wire drive speed 43. This extrusion speed can be measured by observing the condition of the first storage stage 42 since, if the extrusion speed is too low, compared to the speed of drive 43, more wire will be withdrawn from the storage stage than enters it, while if extrusion speed is too high, more wire will enter the storage stage than is withdrawn. Thus, the storage stage 42 provides a signal which is a function of the extrusion wire velocity, serving the purpose of block 48 in FIG. 2. Note that any other type of device measuring speed differences could be used. This signal is then used to control the extrusion pressure control 41 to increase or decrease extrusion pressure in order to increase or decrease extrusion speed, as demanded to match the positive wire drive speed. As will be later seen, this signal may also be used to increase or decrease the draw stress applied to the wire.

In a similar manner, a signal is derived by mechanism 49 from storage stage 45 to increase or decrease the peripheral speed of the wire reeling device 46 to match the speed of the positive wire drive 43.

The use of capstan 56 (FIG. 3) eliminates the need to match the instantaneous extrusion speed of the wire to the instantaneous coiling speed. It is equally important that the drawing tension in the wire between the extruder and capstan is made independent of the tension between the capstan and reeler. Thus, the control system is applicable to extremely delicate extruded materials which might break under a force of as low as 1 gram and which may be undesirably deformed by the use of excessive reeling tension.

FIG. 3 shows one physical arrangement which can be used to form portions of the control system of FIG. 2. In FIG. 3, the die 15, a protion of billet 14, idler 30, coiler 32 and motors 23 and 33, all of FIG. 1, are again shown. The control system embodiment of FIG. 3 includes rotatable wheels 50 and 53, having fixed axes, and movable wheels 54 and 55 (which may move vertically and against the biasing force due to gravity). A positively driven capstan 56, driven by motor 57 under the influence ofa suitable speed control 58, has the extruded wire wound thereon. It pulls frictionally the wire in the direction of the arrows between components and 56.

The extruded wire from die 15 is then threaded around the various wheels 50 and 55 and capstan 56 as shown, where wheels 50 and 55 rotate with relatively low friction. It will be apparent that the wheels 50 and 51 and movable wheel 54 define the first moving wire storage stage 42 of FIG. 2, while the wheels 52, 53 and movable wheel 55 define the second moving wire storage stage 45 of FIG. 2. Note that structure can be provided to enable wheels 54 and 55 to move in any desired direction relative to wheels 50-51 and 52-53 respectively, to provide a fast, accurate response in increasing or decreasing storage and in controlling drawing force and reeling tension, as may be desired. As schematically shown in FIG. 3 by dotted lines, the movement of wheel 54, which is functionally related to the difference between velocity v,. of the extruded wire from die 15, and velocity v which is the velocity of the periphery of the positive drive capstan 56, controls the energization of motor 23. Thus, when v. is too low, compared to V wheel 54 moves toward fixed wheels 50 and 51 and the signal derived from this movement causes motor 23 to increase the extrusion pressure in extruder 40 (FIG. 2), thereby to increase I... As will be seen, movement of wheel 54 may also be used to control drawing tension for optimum control of drawing speed. Thus, the mechanism and circuits connecting wheel 54 and motor 23 in FIG. 3 constitute a portion of the velocity function measurement block 48 of FIG. 2. Note that other modes of velocity measurement could be used to develop signals for the control of pump 22 of FIG. 1 or pressure control 41 of FIG. 2.

The movement sensing apparatus of wheel 55 is suitably connected to motor 33, as shown by dotted lines in FIG. 3 so that the coiling or reeling speed r, of the wire on coiler 32 controls coiling speed in order to match coiling speed v, to capstan speed r The mechanism and circuitry coupling wheel 55 to motor 33 constitutes the schematically shown measurement block 49 of FIG. 2. Thus a similar control loop is formed to control the coiling speed v, as was used to control extrusion speed v... It is important to note that by separating control blocks 48-41 and 49-47 respectively from one another, the danger of the controls interfering with the hunting with each other is eliminated.

FIG. 4 shows, in perspective view, a capstan 56 which could be used for the positive drive component of FIGS. 2 and 3. The capstan of FIG. 4 consists of a drum surface 60. The extruded wire is guided toward the surface 60 by eyelet 62 and then encircles surface 60 for two turns, or any sufficient number of turns to insure a tight frictional grip between the extruded wire and the surface 60. The extruded wire then leaves surface 60 through eyelet 63. The motor 57 of FIG. 3 is suitably connected to the drum surface 60 as by connection to shaft 64, so that the drum surface can be rotated in the direction shown. The drum surface 60 is slightly concave or bell shaped. This shape of surface 60, in combination with eyelets 62 and 63, will insure separation of the loops of wire on the drum surface 60.

It should be understood that other drive mechanisms could be used in place of capstan 56. By way of example, fluid propellant means could be used in which the wire is passed through a tube having a high speed fluid moving therein which exerts a viscous positive drag on the extruded wire, forcing it to advance at a preset speed.

In order to provide tension on the wire in the dancer stages, controlled force may be applied to the movable wheel by means of various electrical, electromechanical and mechanical schemes which would be well known to one skilled in the art. Thus, in FIG. 5, which shows the storage stage including wheels 50, 51 and 54, the wheel 54 has a low mass shaft which carries an underslung weight 71. Note that weight 71 could be replaced by mechanical spring which would give a controlled increase in draw force when v becomes less than v Similarly, magnetic or electromagnetic or electrostatic means may be provided for generating a controlled force which can be varied on a programmed command basis. The ends of shaft 70 then move between spaced stationary guide pairs 72-73 and 74-75, respectively. Obviously, the storage stage, including wheel 55 of FIG. 3, can be constructed in the same manner as that described above.

FIG. 6 shows one possible embodiment of a transducer mechanism and circuit for converting the motion of wheel 54 (or of wheel 55) into an output control voltage. Thus, in FIG. 6, shaft 70, carrying wheel 54, has a potentiometer wiper arm 80 connected thereto which makes sliding electrical connection to resistance strip 81. Two fixed resistors 82 and 83, with the resistor sections of strip 81 on either side of slider 80, then define a bridge circuit. An input voltage is then applied to input terminals 84 and 85 and the output at output terminals 86 and 87 is functionally related to the height of wheel 54 and thus the state of the wire storage stage. This output is then applied to conventional control circuits for the control of motor 23 in the case of the first storage stage (stage 42 of FIG. 2), or for the control of motor 33 for the case of the second storage stage (stage 45 of FIG. 2).

FIG. 7 reproduces certain aspects of the apparatus of FIG. 3 and shows billet 14 extruded through die with wire then taken over wheel 30 to the dancer consisting of wheels 50, 51 and 54. Billet 14 in FIG. 7 is extruded through die 15 at a greater or lesser speed dependent upon increase and decrease, respectively, of the pressure in chamber 21 (FIG. 1). FIG. 7 further illustrates in block diagram form the extrusion speed transducer 110 shown in detail in FIG. 6, whereby the mechanical motion of wheel 54, which is the movable wheel of the storage stage shown, is converted into an output signal at terminals 86 and 87. The output signal appearing at terminals 86 and 87 is connected to the input ofa suitable amplifier 111, the output of which is connected, for example, to the field winding 112 of the speed control drive motor 23 (also shown in FIG. 1 which is connected to the pump 22.

Pump 22 is connected to pressure chamber 21 through a suitable control valve 115 with a conventional accumulator 114 providing a reservoir of fluid between the pump 22 and the pressure chamber 21. A second valve 116 is provided to allow the relief of pressure in chamber 21.

When wheel 54 moves upwardly because of too low an extrusion speed, or downwardly because of too high an extrusion speed, appropriate output signals will be generated at terminals 86 and 87 which will, in turn, respectively increase or decrease the speed of motor 23, thereby adjusting output pressure ofpump 22. This will then increase or decrease the pressure in chamber 21 to adjust the extrusion speed toward a match with the speed set by the positive wire drive of FIG. 3.

Simultaneously with the direct electrical control mode stated above, fluid control systems are also used in which electrically operable valves 115 and 116 control the fluid pressure applied to chamber 21 from the pump 22. Valves 115 and 116 are suitably controlled by servo-motors 117 and 118, respectively, which are, in turn, operated by the output signal at terminals 86 and 87 of the transducer circuit 110. Thus, valves 115 and 116 open and close appropriately as the control circuit calls for greater or lesser extrusion speed.

In the foregoing, the extrusion speed control was adjusted essentially through the adjustment of the extrusion press pressure. It has been found that better control characteristics can be obtained when the adjustment of press pressure is augmented by further adjustment of pulling force applied to the extruded wire.

Note that in the foregoing figures the pulling force is held appropriately constant and is determined for the most part by the force of the mass 71 of the movable portions of the first storage stage. In accordance with an important aspect of the invention, the draw or pulling force on the wire is also varied to cause a desired change in extrusion speed.

FIG. 8 schematically illustrates one arrangement wherein pulling force will automatically change to correct extrusion speed in a proper direction at least during steady state operation. Thus, in FIG. 8, the force tending to pull billet 14 through die 15 will be set essentially by the force of mass 71 (FIG. 5) which can be considered as essentially the total force which pulls wire through the die 15. In order to adjust pulling force, the storage stage dancer loop is formed in V shape such that each of the strands 120 and 121 of the wire on either side of wheel 54 form an angle A with a vertical line 122. Consequently, if the speed decreases relative to the positive drive speed v the wire stored in the storage stage will shorten so that wheel 54 moves upwardly. This upward movement, however, will increase the tension in strands 120 and 121 inversely with the cosine A. Therefore, a decrease in the speed n. automatically causes an increase in the pulling force on the wire being extruded, which will tend to increase the extrusion speed. Ifthe speed v increases relative to the positive drive speed v the converse will happen: more wire will be stored in the storage stage so that the angle A will decrease with a consequent decrease in the pulling force on the wire which would tend to decrease extrusion speed.

Therefore, by using a storage stage providing functionally responsive characteristics similar to the V- shaped loop of FIG. 8, in combination with the novel capstan type arrangement which isolates extrusion conditions from coiling conditions, it becomes possible to adjust extrusion speed through the automatic adjustment of pulling force.

While the correction of extrusion speed in FIG. 8 by adjustment in pulling force can be used alone, it preferably augments control of pressure chamber conditions and extrusion pressure, as shown in connection with FIG. 7. Note that the automatic correction of pulling force in FIG. 8 occurs without any time lag, which lag is inherent in the pressure correction arrangement in FIG. 7.

It should be noted that other types of pulling force augmentation mechanisms could be used in the apparatus and process of the invention, other than the V- shaped dancer arrangement of FIG. 8. By way of example, the viscous drive force of a rapidly moving fluid in a tube surrounding the wire as it exits from the extrusion press could be appropriately controlled, with the first wire storage stage having any conventional structure. Similarly, a controlled force could be applied to the lower wheel 54 (of FIG. 3) or a controlled drive could be applied to wheel 50 of FIG. 3, which can be adjusted to modify pulling force, with changes in extrusion speed.

While the invention herein has been described primarily in connection with controls for hydrostatic extrusion, it should be noted that the control system per se could also be applicable to other processes for ban dling thin and fragile fibers, of any desired material including metals, textile strands, and the like, wherein it is desirable to isolate coiling forces from forces used to pull the filament from its production apparatus. Thus, this permits the use of highly controlled forces for pulling the filament or fibers being produced from the production system while allowing completely different force systems to be used for the coiling.

Although this invention has been described with respect to preferred embodiments, it should be understood that many variations and modifications will now be obvious to those skilled in the art, and, therefore, the scope of this invention is to be limited, not by the specific disclosure herein, but only by the appended claims.

I claim:

1. An augmented hydrostatic extrusion apparatus comprising, in combination:

hydrostatic extrusion press means for extruding therefrom, under relatively high pressure, a thin wire;

pressure control means connected to said press means for controlling the extrusion pressure within said press means, thereby to control the speed of extrusion of said wire;

a positive drive means operatively connected to said wire for moving said wire away from said press means at given velocity;

a wire reeling stage for receiving wire which has passed through said positive drive means for coiling said wire onto a reel;

a reservoir stage disposed between said press means and said positive drive means for receiving and storing a variable length of said wire therein as said wire moves from said press means to said reservoir stage;

extrusion velocity measuring means for measuring a difference between the extrusion velocity of said wire and the said given velocity;

variable pulling force exerting means for providing a positive pulling force on said wire which leaves said press means, thereby to reduce the necessary hydrostatic pressure needed to cause the escape of wire from the die;

means connecting said variable pulling force exerting means to said extrusion velocity measuring means to increase pulling force responsive to a decrease in extrusion speed of said wire relative to said given speed, and to decrease pulling force responsive to an increase in extrusion speed of said wire relative to said given speed and a second reservoir stage disposed between said positive drive means and said wire reeling stage; and means responsive to the loading and unloading of said second reservoir stage for respectively increasing and decreasing the speed of reeling in said wire reeling stage.

2. The apparatus of claim 1 wherein said extrusion velocity measuring means is further connected to said pressure control means for increasing and decreasing press pressure in response to a respective decrease and increase in extrusion velocity of said extruded wire.

3. The apparatus of claim 1 wherein said reservoir comprises at least a first fixed wheel and a second wheel relatively movable with respect to said first wheel; and a biasing means for biasing said second wheel in a given direction; wire extending from said press means and over said first and second wheels, and exerting a force in a direction opposite to said first direction; said biasing means having an increasing biasing force as said second wheel moves in said opposite direction, and having a decreasing biasing force as said wheel moves in said given direction.

4. A control system for controlling the high speed formation of a continuous elongated filament by a filament producing apparatus and for coiling the elongated filament on a reeling apparatus; said filament producing apparatus including first control means operable to vary the speed of production of said filament; said reeling apparatus including second control means operable to vary the speed of coiling of said filament; said control system including first and second filament storage stages for continuously receiving and issuing therefrom said filament and containing variable lengths of filament, dependent upon the relative speeds of reception and issuance therefrom of said filament, positive drive means for engaging and driving said filament with a given speed, first and second means operatively connected to said filament for measuring functions of said speed of production of said filament and said speed of coiling of said filament respectively as compared to said given speed of said positive drive means and for producing output control signals related to said functions, and means connecting said first and second means to said first and second control means, thereby to independently control and closely synchronize said speeds of production and of coiling with the said given speed of said positive drive means; said first storage stage being connected between said filament producing apparatus and said positive drive means and carrying said filament from said filament producing apparatus to said positive drive means; said second storage stage being connected between said positive drive means and said reeling apparatus and carrying said filament from said positive drive means to said reeling apparatus; said first control means including means for varying the force for pulling filament from said elongated filament producing apparatus.

5. The control system of claim 4 wherein said filament producing apparatus comprises a hydrostatic extrusion apparatus and wherein said filament constitutes a metallictype wire.

6. The control system of claim 4 wherein said first and second storage stages constitute reservoir assemblies having respective movable wheels with means biasing said wheels in a given direction over which said filament passes, with the tension of said filament pressing said wheels in a direction opposite said given direction.

7. The control system of claim 5 wherein said filament constitutes a metallic wire having a diameter of less than about 10 mils.

8. The control system of claim 5 wherein said first control means further includes means for controlling the pressure of extrusion of said extrusion apparatus.

9. The control system of claim 6 wherein the force of gravity constitutes said biasing means.

10. The control system of claim 6 wherein said means biasing said movable wheel of said first storage stage develops an increasing biasing force as said lastmentioned movable wheel moves in said opposite direction and having a decreasing biasing force as said wire moves from said last-mentioned wheel in said given direction.

11. A control system for controlling the high speed formation of a continuous elongated filament by a filament producing apparatus and for coiling the elongated filament on a reeling apparatus; said filament producing apparatus including first control means operable to vary the speed of production of said filament; and reeling apparatus including second control means operable to vary the speed of coiling of said filament; said control system including first and second filament storage stages for continuously receiving and issuing therefrom said filament and containing variable lengths of filament, dependent upon the relative speeds of reception and issuance therefrom of said filament, positive drive means for engaging and pulling said filament with a given speed, first and second means operatively connected to said filament for measuring functions of said speed of production of said filament and said speed of coiling of said filament respectively as compared to said given speed of said positive drive means and for producing output control signals related to said functions, and means connecting said first and second means to said first and second control means, thereby to independently control and closely synchronize each of said speeds of production and of coiling with the speed of said positive drive means; said first storage stage being connected between said filament producing apparatus and said positive drive means and carrying said filament from said filament producing apparatus to said positive drive means; said second storage stage being connected between said positive drive means and said reeling apparatus and carrying said filament from said positive drive means to said reeling apparatus.

12. The control system of claim 11 wherein said filament producing apparatus comprises a hydrostatic extrusion apparatus and wherein said filament constitutes a metallictype wire.

13. The control system of claim 11 wherein said first and second storage stages constitute reservoir assemblies having respective movable wheels with means biasing said wheels in a given direction over which said filament passes, with the tension of said filament pressing said wheels in a direction opposite said given direction.

14. The control system of claim 11 wherein said positive drive means comprises a capstan having a drum surface on which said filament is wrapped to frictionally engage said drum surface, and drive motor means for rotating said drum surface.

15. The control system of claim 12 wherein said filament constitutes a metallic-type wire having a diameter of less than about mils.

16. The control system of claim 12 wherein said filament constitutes a metallic-type wire having a diameter of less than about 1.0 mil and a yield strength of less than about 100 grams.

17. The control system of claim 12 wherein said filament constitutes a metallic-type wire having a diameter ofless than about 10 mils and having a high surface finish substantially free of longitudinal die marks.

18. The control system ofclaim 12 wherein said first control means constitutes means for controlling the pressure of extrusion of said extrusion apparatus.

19. The control system of claim 13 wherein said biasing means constitutes the force of gravity.

20. The control system of claim 13 wherein said first and second means for measuring said functions of filament production speed and coiling speed respectively are operatively connected to said movable wheels.

21. The control system ofclaim 12 wherein said first and second storage stages constitute reservoir assemblies having respective movable wheels with means biasing said wheels in a given direction over which said filament passes, with the tension of said filament pressing said wheels in a direction opposite said given direction.

22. The control system of claim 13 wherein said positive drive means comprises a capstan having a drum surface on which said filament is wrapped to frictionally engage said drum surface, and drive motor means for rotating said drum surface.

23. The control system of claim 22 wherein said filament constitutes a metallic wire having a diameter of less than about 1.0 mil and a yield strength of less than about grams.

24. The control system of claim 23 wherein said first control means constitutes means for controlling the pressure of extrusion of said extrusion apparatus.

25. The process of continuously controlling extrusion of thin wire from a hydrostatic extrusion press and coiling said wire on a reel; said process comprising:

passing said thin wire from said extrusion press into a first reservoir stage,

and thereafter exerting a positive pulling force on the wire coming out of said first reservoir stage to drive said wire at a given speed,

and thereafter passing said wire into a second reservoir stage; and thereafter passing said wire from said second reservoir stage and winding said wire onto said reel.

and varying the speed of extrusion of said wire from said extrusion press to match the speed of said wire to said given speed defined by said positive drive force,

and independently varying the speed of rotation of said reel to match the coiling velocity of said wire at the periphery of said reel to said given speed.

26. The process of claim 25 in which control signals for varying extrusion speed and coiling speed are derived from said first and second reservoir stages respectively.

27. The process of claim 26 in which said speed of extrusion is controlled by controlling the extrusion pressure of said press, while maintaining a substantially constant pulling force for pulling said wire from said extrusion press. 

1. An augmented hydrostatic extrusion apparatus comprising, in combination: hydrostatic extrusion press means for extruding therefrom, under relatively high pressure, a thin wire; pressure control means connected to said press means for controlling the extrusion pressure within said press means, thereby to control the speed of extrusion of said wire; a positive drive means operatively connected to said wire for moving said wire away from said press means at given velocity; a wire reeling stage for receiving wire which has passed through said positive drive means for coiling said wire onto a reel; a reservoir stage disposed between said press means and said positive drive means for receiving and storing a variable length of said wire therein as said wire moves from said press means to said reservoir stage; extrusion velocity measuring means for measuring a difference between the extrusion velocity of said wire and the said given velocity; variable pulling force exerting means for providing a positive pulling force on said wire which leaves said press means, thereby to reduce the necessary hydrostatic pressure needed to cause the escape of wire from the die; means connecting said variable pulling force exerting means to said extrusion velocity measuring means to increase pulling force responsive to a decrease in extrusion speed of said wire relative to said given speed, and to decrease pulling force responsive to an increase in extrusion speed of said wire relative to said given speed and a second reservoir stage disposed between said positive drive means and said wire reeling stage; and means responsive to the loading and unloading of said second reservoir stage for respectively increasing aNd decreasing the speed of reeling in said wire reeling stage.
 2. The apparatus of claim 1 wherein said extrusion velocity measuring means is further connected to said pressure control means for increasing and decreasing press pressure in response to a respective decrease and increase in extrusion velocity of said extruded wire.
 3. The apparatus of claim 1 wherein said reservoir comprises at least a first fixed wheel and a second wheel relatively movable with respect to said first wheel; and a biasing means for biasing said second wheel in a given direction; wire extending from said press means and over said first and second wheels, and exerting a force in a direction opposite to said first direction; said biasing means having an increasing biasing force as said second wheel moves in said opposite direction, and having a decreasing biasing force as said wheel moves in said given direction.
 4. A control system for controlling the high speed formation of a continuous elongated filament by a filament producing apparatus and for coiling the elongated filament on a reeling apparatus; said filament producing apparatus including first control means operable to vary the speed of production of said filament; said reeling apparatus including second control means operable to vary the speed of coiling of said filament; said control system including first and second filament storage stages for continuously receiving and issuing therefrom said filament and containing variable lengths of filament, dependent upon the relative speeds of reception and issuance therefrom of said filament, positive drive means for engaging and driving said filament with a given speed, first and second means operatively connected to said filament for measuring functions of said speed of production of said filament and said speed of coiling of said filament respectively as compared to said given speed of said positive drive means and for producing output control signals related to said functions, and means connecting said first and second means to said first and second control means, thereby to independently control and closely synchronize said speeds of production and of coiling with the said given speed of said positive drive means; said first storage stage being connected between said filament producing apparatus and said positive drive means and carrying said filament from said filament producing apparatus to said positive drive means; said second storage stage being connected between said positive drive means and said reeling apparatus and carrying said filament from said positive drive means to said reeling apparatus; said first control means including means for varying the force for pulling filament from said elongated filament producing apparatus.
 5. The control system of claim 4 wherein said filament producing apparatus comprises a hydrostatic extrusion apparatus and wherein said filament constitutes a metallictype wire.
 6. The control system of claim 4 wherein said first and second storage stages constitute reservoir assemblies having respective movable wheels with means biasing said wheels in a given direction over which said filament passes, with the tension of said filament pressing said wheels in a direction opposite said given direction.
 7. The control system of claim 5 wherein said filament constitutes a metallic wire having a diameter of less than about 10 mils.
 8. The control system of claim 5 wherein said first control means further includes means for controlling the pressure of extrusion of said extrusion apparatus.
 9. The control system of claim 6 wherein the force of gravity constitutes said biasing means.
 10. The control system of claim 6 wherein said means biasing said movable wheel of said first storage stage develops an increasing biasing force as said last-mentioned movable wheel moves in said opposite direction and having a decreasing biasing force as said wire moves from said last-mentioned wheel in said given direction.
 11. A control systeM for controlling the high speed formation of a continuous elongated filament by a filament producing apparatus and for coiling the elongated filament on a reeling apparatus; said filament producing apparatus including first control means operable to vary the speed of production of said filament; and reeling apparatus including second control means operable to vary the speed of coiling of said filament; said control system including first and second filament storage stages for continuously receiving and issuing therefrom said filament and containing variable lengths of filament, dependent upon the relative speeds of reception and issuance therefrom of said filament, positive drive means for engaging and pulling said filament with a given speed, first and second means operatively connected to said filament for measuring functions of said speed of production of said filament and said speed of coiling of said filament respectively as compared to said given speed of said positive drive means and for producing output control signals related to said functions, and means connecting said first and second means to said first and second control means, thereby to independently control and closely synchronize each of said speeds of production and of coiling with the speed of said positive drive means; said first storage stage being connected between said filament producing apparatus and said positive drive means and carrying said filament from said filament producing apparatus to said positive drive means; said second storage stage being connected between said positive drive means and said reeling apparatus and carrying said filament from said positive drive means to said reeling apparatus.
 12. The control system of claim 11 wherein said filament producing apparatus comprises a hydrostatic extrusion apparatus and wherein said filament constitutes a metallictype wire.
 13. The control system of claim 11 wherein said first and second storage stages constitute reservoir assemblies having respective movable wheels with means biasing said wheels in a given direction over which said filament passes, with the tension of said filament pressing said wheels in a direction opposite said given direction.
 14. The control system of claim 11 wherein said positive drive means comprises a capstan having a drum surface on which said filament is wrapped to frictionally engage said drum surface, and drive motor means for rotating said drum surface.
 15. The control system of claim 12 wherein said filament constitutes a metallic-type wire having a diameter of less than about 10 mils.
 16. The control system of claim 12 wherein said filament constitutes a metallic-type wire having a diameter of less than about 1.0 mil and a yield strength of less than about 100 grams.
 17. The control system of claim 12 wherein said filament constitutes a metallic-type wire having a diameter of less than about 10 mils and having a high surface finish substantially free of longitudinal die marks.
 18. The control system of claim 12 wherein said first control means constitutes means for controlling the pressure of extrusion of said extrusion apparatus.
 19. The control system of claim 13 wherein said biasing means constitutes the force of gravity.
 20. The control system of claim 13 wherein said first and second means for measuring said functions of filament production speed and coiling speed respectively are operatively connected to said movable wheels.
 21. The control system of claim 12 wherein said first and second storage stages constitute reservoir assemblies having respective movable wheels with means biasing said wheels in a given direction over which said filament passes, with the tension of said filament pressing said wheels in a direction opposite said given direction.
 22. The control system of claim 13 wherein said positive drive means comprises a capstan having a drum surface on which said filament is wrapped to frictionally engage said drum surface, and drive motor means For rotating said drum surface.
 23. The control system of claim 22 wherein said filament constitutes a metallic wire having a diameter of less than about 1.0 mil and a yield strength of less than about 100 grams.
 24. The control system of claim 23 wherein said first control means constitutes means for controlling the pressure of extrusion of said extrusion apparatus.
 25. The process of continuously controlling extrusion of thin wire from a hydrostatic extrusion press and coiling said wire on a reel; said process comprising: passing said thin wire from said extrusion press into a first reservoir stage, and thereafter exerting a positive pulling force on the wire coming out of said first reservoir stage to drive said wire at a given speed, and thereafter passing said wire into a second reservoir stage; and thereafter passing said wire from said second reservoir stage and winding said wire onto said reel, and varying the speed of extrusion of said wire from said extrusion press to match the speed of said wire to said given speed defined by said positive drive force, and independently varying the speed of rotation of said reel to match the coiling velocity of said wire at the periphery of said reel to said given speed.
 26. The process of claim 25 in which control signals for varying extrusion speed and coiling speed are derived from said first and second reservoir stages respectively.
 27. The process of claim 26 in which said speed of extrusion is controlled by controlling the extrusion pressure of said press, while maintaining a substantially constant pulling force for pulling said wire from said extrusion press. 